Linux Format forums

[pc]

Solaris by default has a true "sh" shell.
Linux by default seems to have the sh shell as link to the bash shell.

If I want to write a truely portable script, I would like to ensure that it is "sh" compatible, and does not use any of the extra features from bash.

Can anyone advise of a way of writing a true sh script on linux, that does not seem to come with a true sh shell?

[RD]

google??
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[Nigel]

Actually, Solaris has several shells available, including bash. It's installed by default with Solaris-10, although it may not be available for previous versions.
So if you write a bash script and make sure it has the line

[nelz]

When bash is executed through the sh link, it behaves as sh. I generally write scripts with a /bin/sh shebang line unless it uses something bash-specific.
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[pc]

Thanks for the replies. The solaris is version 9 and bash is not I believe a default.

I didn't realise that bash through an sh link behaves like sh. How does it do that? How does it know it being called through a link with the name "sh" and so behaves differently?

Quick look at man bash gives:
If bash is invoked with the name sh, it tries to mimic the startup
behavior of historical versions of sh as closely as possible, while
conforming to the POSIX standard as well.

Guess I should have read the help more thoroughly, apologies.

So the simple answer seem to be to start the script with:

#!/bin/sh

and on linux it will interpret it as "true" sh, even though /bin/sh is a link to /bin/bash.

[nelz]

[Steogede]

[pc]

nelz,

Thnaks for the explanation. I did indeed create a script and a soft link to that script. $0 was the script name when run directly, and the link name when run via the link. Previously I had taken $0 to always be the script name, which I can see now is not always the case.